Hi Ravi Try the series modulator: If the VCO is running off X Vcc, for full 100 percent mod, use 2X Vcc for the modulator. For low power, it is just a darlington or a high Hfe medium power NPN in emitter follower config, with base biased to 1/2Vcc for no mod in. Apply audio signal to base of darlington (couple with a 10uF in series) and the emitter goes to Vcc of VCO. So if VCO Vcc is 6V, use 12V as Vcc for the Collector of modulator, bias base at appx 7V, with a divider say 82K up 100K down, take modln output from emitter and feed to Vcc of VCO, preferably after the buffer to prevent VCO pulling. A single transistor mic preamp can drive the Base of the darlington. agoogle search on series AM modulator should give you a plethora of ideas..... 73 Ron VU2ORO Indirapuram, NCR --- On Tue, 3/8/11, Ravi Miranda <ravimiranda@gmail.com> wrote:
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